Hybrid solar heat power generation device

ABSTRACT

Lower heat-collection efficiency and a much smaller amount of solar heat may result from the providing of only a single receiver on a supporting post to collect lights coming from both heliostats located at nearby positions and heliostats located at faraway positions. A solar heat power generation device to be provided by the invention can avoid such problems. The solar heat power generation device has the following characteristic features. The solar heat power generation device comprises: a supporting post  4  including a receiver  1  that receives sunlight; and a plurality of heliostats  6  which are provided concentrically around the supporting post  4  and which reflect the sunlight towards the receiver  1 . The supporting post  4  includes at least two receivers  1   a  and  1   b  that are arranged in the up-and-down direction. The receiver  1   a  provided at an upper-side position receives reflected lights L 1  coming from the heliostats  6   a  located at faraway positions, and the receiver  1   b  provided at a lower-side position receives reflected lights L 2  coming from the heliostats  6   b  located at nearby positions.

TECHNICAL FIELD

The present invention relates to a power generation device using solar heat. More specifically, the present invention relates to a solar heat power generation device which is capable of increasing the light collection efficiency for the light reflected by heliostats and which is thus capable of enhancing the power-generation efficiency.

BACKGROUND ART

Recently, there has been an increase in interest in the global environments such as: global warming caused by exhaust gas produced by the combustion of fossil fuels; and the depletion of fossil fuels. In addition, alternative energy that may replace the aforementioned fossil fuels has attracted more public attention. For such alternative energy, wind power generation and photovoltaic power generation have been spreading.

Meanwhile, there is a concentrating-type solar heat power generation device in which a heat-transfer medium is heated by use of heat produced by concentrating solar rays, steam is produced by the heat of the heat-transfer medium, a steam turbine is driven by the steam, and consequently electric power is generated. The device has attracted public attention because the device can be operated with similar power-generating facilities to those for the conventional thermal power station and can achieve a high output level.

Various types of concentrating-type solar heat power generation devices have been proposed thus far, including a trough-type solar heat power generation device (see, for example, Patent Document 1), a dish-type solar heat power generation device (see, for example, Patent Document 3), and a tower-type solar heat power generation device (see, for example, Patent Document 2). The trough-type device includes: reflectors each having a semi-circular sectional shape and having a light-reflecting surface formed in one surface thereof; and pipes extending in the axial directions of the respective reflectors, and a heat-transfer medium is introduced into the pipes. The tower-type device includes: a tower placed at the center and provided with a heat-transfer-medium heating portion on a top portion thereof; and multiple heliostats placed around the tower. The dish-type device includes: a bowl-shaped reflector having a light-reflecting surface formed in one surface thereof; and a heat-transfer-medium heating portion provided near the reflector.

In addition, a beam-down-system solar heat power generation device has been proposed (see, for example, Non-Patent Document 1). The beam-down-system solar heat power generation device includes a large number of heliostats arranged around the center; a heat-transfer medium heating unit provided in a lower portion; and a curved reflector mirror (center reflector) provided above the heat-transfer-medium heating unit.

Patent Document 1: WO2005/017421

Patent Document 2: Japanese patent application Kokai publication No. 2004-169059.

Patent Document 3: Japanese patent application Kokai publication No. 2005-106432.

Non-Patent Document 1: Solar Energy, Volume 62, Number 2, February 1998, pp. 121-129 (9)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention (Trough Type)

The reflector of the trough-type solar heat power generation device has quite a large dimension in the width direction of the reflector. A large number of reflectors are arranged in lines and rows, and cause a problem that the solar heat power generation device needs quite a large area to install the reflectors.

(Dish Type)

The dish-type solar heat power generation device is a compact-sized device because each reflector dish collects the sunlight and heats the heat-transfer medium. There is a limit to the size of each reflector dish. Accordingly, the dish-type solar heat power generation device has a problem of being inappropriate for mass-scale power generation.

(Tower Type)

The tower-type solar heat power generation device has the following problem. As FIG. 9 shows, a receiver 105 has a light-receiving surface 105 a irradiated with a reflected light R109, a light coming from each heliostat 102 that is located away from a tower 100. The incident angle θ1 of the reflected light R109 into the light-receiving surface 105 a is approximately a right angle. Such an incident angle θ1 decreases the area irradiated with the reflected light R109, and increases the amount of light per unit area. The illuminance is thus enhanced and the higher illuminance results in a larger amount of heat collected by each heliostat 102. The light-receiving surface 105 a is irradiated also with a reflected light R108, a light coming from each heliostat 101 that is located close to the tower 100. The incident angle θ2 of the reflected light R108 into the light-receiving surface 105 a is an acute angle. Such an incident angle θ2 increases the area irradiated with the reflected light R108, and decreases the amount of light per valley area. The illuminance is thus lowered down and the lower illuminance results in a smaller amount of heat collected by each heliostat 101.

Assuming that the heat-reception efficiency is represented by sin θ (incident angle), the heat-reception efficiency for each heliostat 102 located at the faraway position is approximately 100%, and that for each heliostat 101 located at the nearby position is approximately 50%.

(Beam-Down Type)

The beam-down solar heat power generation device has the following problem. As shown in FIG. 10, a center reflector 116 has a reflection surface 116 a. A reflected light R119, alight coming from each heliostat 112 that is located far away from the center reflector 116 enters the reflection surface 116 a at an acute incident angle. To put it differently, the reflected light R109 enters the center reflector 116 in a quite oblique manner. Such an oblique incidence of the reflected light R119 results in a larger area of the center reflector 116 irradiated with the reflected light R119 coming from each heliostat 112 that is located at the faraway position. Consequently, the heat-collection efficiency becomes lower.

In addition, even when the heliostats are provided in an area having a radius of approximately several hundreds of meters, the center reflector must have an approximately 100-m diameter. A center reflector of this size may weigh several hundreds of tons. Such a heavy center reflector poses a problem of the strength of the structure for supporting the center reflector.

(Present Invention)

In view of the aforementioned problems that the conventional techniques have, an object of the present invention is to provide a solar heat power generation device capable of achieving a higher illuminance by reducing the area of the receiver irradiated with the reflected light which is cast, onto the receiver, by each heliostat located close to the receiver and with the reflected light which is cast, onto the receiver, by each heliostat located far away from the receiver.

Means for Solving the Problems

A hybrid solar heat power generation device according to the present invention has the following configuration.

1) The solar heat power generation device includes: a supporting post including a receiver that receives sunlight; and a plurality of heliostats which are provided so as to surround the supporting post coaxially and which reflect the sunlight towards the receiver. The solar heat power generation device is characterized in that the supporting post includes at least two receivers that are arranged in the up-and-down direction, the receiver provided at an upper-side position receives reflected lights coming from the heliostats located at faraway positions, and the receiver provided at a lower-side position receives reflected lights coming from the heliostats located at nearby positions.

2) The solar heat power generation device is characterized in that, when the light intensity of a reflected light received by a receiver with a 90-degree incident angle is 100%, each of the receivers receives the reflected lights coming from heliostats located at positions such that a light intensity of 60% or higher is achieved by each reflected light received by the corresponding receiver.

3) The solar heat power generation device is characterized in that an incident angle of the reflected light reflected by each heliostat located far away from the supporting post towards the receiver provided at the upper-side position is set at 75° to 105°, and an incident angle of the reflected light reflected by each heliostat located near the supporting post towards the receiver provided at the lower-side position is set at 75° to 105°.

4) The solar heat power generation device includes: a supporting post including receivers that receive sunlight; and a plurality of heliostats which are provided so as to surround the supporting post coaxially and which reflect the sunlight towards the receivers. The solar heat power generation device is characterized in that one of the receivers is provided at an upper-side position on the supporting post, the one receiver receiving reflected lights coming from the heliostats located at faraway positions, and a center reflector is provided at a lower-side position on the supporting post, the center reflector receiving reflected light coming from the heliostats located near the supporting body, and another one of the receivers is provided below the center reflector, the other receiver receiving the sunlight having been reflected by the center reflector.

5) The solar heat power generation device is characterized in that at least three supporting posts are assembled together to form a pyramid shape, a columnar body is provided so as to extend upwards from upper-end sides of the supporting posts, a center reflector is fixed to the supporting posts that have been assembled together to form the pyramid shape, in addition, receivers are provided below the center reflector and on the columnar body, the receiver provided on the columnar body receives reflected lights coming from heliostats provided far away from the supporting posts, and the center reflector receives reflected lights coming from heliostats provided near the supporting posts, and the receiver provided on the supporting posts receives the lights passed on to the receiver by the center reflector.

6) The solar heat power generation device includes: the supporting post equipped with the center reflector; and the plurality of heliostats provided so as to surround the supporting post. The solar heat power generation device is characterized by including: a frame formed in an arc shape that fits a wall surface of the center reflector having a semicircular arc sectional shape, the frame having one of its ends supported by the supporting post; a cleaning robot which is attached to the frame so as to be capable of moving along the frame; and moving means for moving the frame with the cleaning robot in a circumferential direction of the center reflector; and the solar heat power generation device characterized in that the cleaning robot includes a spray device that sprays a cleaning liquid onto the wall surface of the center reflector.

7) The solar heat power generation device is characterized in that the receiver provided below the center reflector includes a cone-shaped light receiving portion, and dust-prevention means for allowing the transmission of the sunlight therethrough but for blocking entry of dust such as sand is provided to cover a light entrance for the sunlight formed in the light receiving portion.

8) The solar heat power generation device is characterized in that a receiver is provided at an upper-side position on a supporting post so as to receive the reflected lights from a plurality of heliostats provided concentrically around the supporting post, and the light receiving surface of the receiver is formed in a bowl-like shape so that the incident angle of the reflected light coming from each of the plurality of heliostats can be either a right angle or an angle close to a right angle with respect to the light receiving surface.

EFFECTS OF THE INVENTION

1) In the solar heat power generation device, the receiver provided at an upper-side position on the supporting post receives the reflected lights coming from the heliostats located at faraway positions whereas the receiver provided at a lower-side position on the supporting post receives the reflected lights coming from the heliostats located at nearby positions. In addition, the light receiving plate of each receiver has a depression angle so that the reflected light coming from each receiver can form either a right angle or an angle close to a right angle with the light receiving plate. Accordingly, an incident angle of 90° or of an angle close to 90° with the light receiving plate of each receiver is achieved by each of the corresponding reflected lights coming from the heliostats located in an area extending from positions close to the supporting post to positions far away from the supporting post. With such an incident angle, each reflected light entering the corresponding receiver can form a smaller irradiation area, and thereby a higher illuminance can be achieved. The higher illuminance increases the amount of heat received by the receiver, and enhances the heat-exchange efficiency with the molten salt. Consequently, more heat can be generated.

2) The solar heat power generation device use more efficiently the reflected lights coming from the heliostats provided in an area extending from nearby positions to faraway positions. Accordingly, a larger-scale solar heat power generation device can achieve a higher output capacity.

3) The cleaning robot removes sand and dust that adhere to the surface of the center reflector. Though such sand and dust would otherwise make the center reflector reflect light towards the receiver less efficiently, the cleaning robot can prevent such lower efficiency from occurring.

4) Without the dust-prevention means, dust particles such as sand that enter the light receiving portion of the receiver would dirty the surface of the internal wall of the light receiving portion, resulting in lower heat-exchange efficiency with the molten salt. The dust-prevention means can avoid such lower heat-exchange efficiency.

5) Each light receiving plate is formed in a shape that can achieve an incident angle of a 90° or an angle close to 90° for each of the reflected lights cast onto the light receiving plate of the corresponding receiver by the heliostats provided in an area extending from the nearby positions to the faraway positions. Such an incident angle increases the amount of heat collected by each receiver, resulting in an increase in the amount of power generation. In addition, an increase can be achieved in the heat-collection efficiency for the reflected lights coming from the heliostats located at faraway positions. Accordingly, a larger-scale solar heat power generation device can be constructed to achieve a higher output capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a solar heat power generation device according to the present invention.

FIG. 2 is a schematic sectional diagram illustrating a receiver of the solar heat power generation device according to the present invention.

FIG. 3 is a chart illustrating the incident angle of the sunlight that is cast onto the receiver and the area irradiated with the sunlight.

FIG. 4 is a chart illustrating the incident angle of the sunlight that is cast onto the receiver and the amount of generated power.

FIG. 5 is a diagram illustrating a solar heat power generation device according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a cleaning apparatus.

FIG. 7 is a diagram illustrating a solar heat power generation device according to a third embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating a receiver of the solar heat power generation device according to the third embodiment of the invention.

FIG. 9 is a schematic diagram illustrating a conventional tower-type solar heat power generation device.

FIG. 10 is a schematic diagram illustrating a conventional beam-down solar heat power generation device.

FIG. 11 is a chart illustrating the amount of generated power and the radius of the area where heliostats are provided.

DESCRIPTION OF SYMBOLS

-   A1, A2, A3 solar heat power generation device -   L sunlight -   L1, L2, L3, L11, L12, L21, L22 reflected light -   c1 short distance section -   c2 middle distance section -   c3 long distance section -   1 a, 1 b, 1 c, 11 a, 12, 21 a, 22 receiver -   4, 14, 24 supporting post -   6 a, 6 b, 6 c, 16 a, 16 b, 26 a, 26 b heliostat -   13, 23 center reflector -   22 a opening portion -   22 b light collecting portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a solar heat power generating device according to the present invention will be described by referring to the drawings.

Embodiment 1

FIG. 1 is a schematic diagram illustrating a solar heat power generation device A1 according to the present invention. The solar heat power generation apparatus A1 includes plural receivers 1 a, 1 b, and 1 c, which are provided on a supporting post 4 and arranged in this order from the top to the bottom. Each of the receivers 1 a, 1 b, and 1 c, is a heat exchanger which absorbs the solar heat and which transfers the heat to a heat-transfer medium. Multiple heliostats 6 (6 a, 6 b, and 6 c) are provided concentrically around the supporting post 4 with the receivers 1 a, 1 b, and 1 c. Each heliostat 6 includes a reflector mirror m made of plural small mirror plates that reflect the sunlight, that is, the solar heat.

As FIG. 2 shows, each receiver 1 includes a heat receiving plate 1 a and a heat-transfer-medium pipe 9. The heat receiving plate 1 a is a cone-shaped member formed by connecting multiple plate-shaped heat absorbers. The heat-transfer-medium pipe 9 is wound around plural times along the internal circumference of the heat receiving plate 1 a. Each heliostat 6 includes a device for tracking the sunlight S and a driving device for driving a reflector mirror m vertically and horizontally. Each heliostat 6 is controlled so as to reflect the sunlight S towards the corresponding receiver 1.

As FIG. 1 shows, the receiver 1 a located at the highest position on the supporting post 4 is designed to receive a reflected light R1 coming from each of the heliostats 6 a located far away from the supporting post 4. The receiver 1 b located at the middle position on the supporting post 4 is designed to receive a reflected light R2 coming from each of the heliostats 6 b located at an intermediate position. The receiver 1 c located at the lowest position on the supporting post 4 is designed to receive a reflected light R3 coming from each of the heliostats 6 c located closely to the supporting post 4.

The incident angle of each of the reflected lights R1, R2, and R3 into the corresponding one of the receivers 1 a, 1 b, and 1 c is adjusted by controlling the angle of the light receiving plate 1 a of each of the receivers 1 a, 1 b, and 1 c. The incident angles are adjusted so that the intensities of their corresponding reflected lights can be equal to or higher than 60%.

Specifically, as FIG. 2 shows, the incident angle of each of the reflected lights R1, R2, and R3 ranges from the lowest incident angle β=75° to the highest incident angle γ=105°. As FIG. 3 shows, the irradiation efficiency of the sunlight that is cast onto the light receiving plate 1 a becomes the highest when the incident angle of the sunlight into the light receiving plate 1 a is 90° (i.e., in the case of perpendicular incidence). As the incident angle becomes either smaller or larger than 90°, the irradiation efficiency decreases rapidly in an exponential fashion. Accordingly, the incident angle is designed to range from 75° to 105° because an incident angle within this range guarantees an intensity of the reflected light that is equal to or higher than 60%.

In addition, the light receiving plate 1 a is attached so as to make a tilt angle α with the axial direction of the supporting post 4. The tilt angle α is adjusted so that the incident angles of the reflected lights R1, R2, and R3 coming from the corresponding heliostats 1 a, 1 b, and 1 c can be within a range from 75° to 105°.

Now, assume that the area formed on the light receiving plate 1 a by the sunlight reflected towards the light receiving plate 1 a when the incident angle 90° is 100. When the incident angle ranges from 75° to 105°, the area formed on the light receiving plate 1 a by the sunlight that is obliquely cast onto the light receiving plate 1 a is no more than 104. Accordingly, even the heliostat that does not cast the sunlight perpendicularly onto the light receiving plate 1 a can have an irradiation efficiency that is equal to or higher than 60%.

In addition, as FIG. 4 shows, since the incident angle of the reflected light that is cast onto the light receiving plate 1 a is restricted within a range from 75° to 105°, even the heliostat whose incident angle of the sunlight cast onto the light receiving plate 1 a deviates most from 90° can have a power-generation efficiency that is equal to or higher than 60%.

As FIG. 4 (illustrating the incident angle and the power-generation efficiency) shows, the incident angle is adjusted within a range from 75° to 105° so that the power-generating efficiency can be equal to or higher than 60%. Accordingly, as FIG. 4 shows, once the incident angle departs from the above-mentioned range, the amount of power generation decreases in an exponential manner. Assuming that the amount of power generation with an incident angle of 90° is 100, even the heliostat whose incident angle of the sunlight cast onto the light receiving plate 1 a deviates most from 90° can keep an amount of power generation that is equal to or larger than 60.

As FIG. 1 shows, the heliostats 6 are divided into groups and are individually adjusted so that the incident angle of each of the reflected lights R1, R2, and R3 into the corresponding one of the receivers 1 a, 1 b, and is can be kept within the above-mentioned range. Specifically, a short distance section C1, a middle distance section C2, and a long distance section C3 are formed in this order from the area closest to the support post 4 outwards. The heliostats 6 a, 6 b, and 6 c are provided in their corresponding sections C1, C2, and C3. The heliostats 6 a, 6 b, and 6 c are adjusted individually so that the sunlight can be cast onto their corresponding predetermined receivers 1 a, 1 b, and 1 c, and, in addition, are adjusted so that the incident angle of each of the reflected lights R1, R2, and R3 that are cast onto their corresponding receivers 1 a, 1 b, and 1 c can be within the above-mentioned range (a range from 75° to 105°).

Specifically, in this embodiment, the heights at which the receivers 1 a, 1 b, and 1 c are positioned are: approximately 105 m for the receiver 1 a for long distance (the height h3); approximately 60 m for the receiver 1 b for middle distance (the height h2); and approximately 30 m for the receiver 1 c for short distance (the height h1). The above-described sections are the long distance section C3, the middle distance section C2 and the short distance section C1 which respectively are approximately 100 m to 400 m, approximately 50 m to 200 m, and approximately 15 m to 60 m, away from the supporting post 4. Accordingly, the incident angle of each of the reflected lights R1, R2, and R3 that are cast onto their corresponding receivers 1 a, 1 b, and 1 c can be kept within a range from 75° to 105°.

In the solar heat power generation device A1 having the above-described configuration, the predetermined receivers 1 a, 1 b, and 1 c receive their corresponding reflected lights R1, R2, and R3 that are cast by the heliostats 6. Thus, the heat-transfer medium (such as a molten salt containing 40% sodium nitride, 7% sodium nitrate, and 53% potassium nitrate, for example) supplied to the receivers 1 a, 1 b, and 1 c is heated up to approximately 500° C. Then, the high-temperature molten salt is introduced into the heat exchanger provided next to the supporting post 4, and generates steam, which drives a turbine power generator to generate electric power.

The molten salt that has been heated up by the receivers is stored in a high-temperature molten-salt tank, and is then sent to the heat exchanger, where the molten salt is used for generating electric power. After that, the molten salt is stored in a low-temperature molten-salt tank. The high-temperature molten-salt tank stores the molten salt of an amount capable of accumulating heat that is enough to generate electric power even while the solar heat is not available, for example, at night. Consequently, electric power can be generated incessantly both day and night.

In this embodiment, plural receivers are provided on the supporting post so that the incident angle of 90° or an angle close to 90° can be achieved by each of the reflected lights that are cast by the heliostats onto their corresponding receivers. Accordingly, the light receiving area on each of the receivers onto which the reflected lights from the corresponding heliostats are cast becomes so small that the illuminance becomes strong. Consequently, the amount of collected solar heat increases so that the amount of heat given to the molten salt increases as well. As a result, more electric power can be generated.

In addition, the larger-scale solar heat power generation device can increase significantly the amount of the collected heat, so that mass-scale power generation can be made possible.

Embodiment 2

In this embodiment, as FIG. 5 shows, a receiver 11 a is provided at a higher position on a supporting post 14 whereas a center reflector 13 and a receiver 12 are provided at lower positions on the supporting post 14. The center reflector 13 is made of multiple reflector mirrors 13 a each of which has a small mirror-plate shape. The multiple reflector mirrors 13 a are collected together to form the bowl-shaped center reflector 13 that has a semicircular-arc sectional shape. The center reflector 13 is fixed by means of either plural cables 13 c or plural hanging means 13 c attached to the supporting post 14.

A heat-collecting recessed portion is formed in the upper surface of the receiver 12 provided at the lower position. The heat-collecting recessed portion accepts the reflected light coming from the center reflector 13. Multiple heat-transfer-medium pipes are provided so as to surround the recessed portion, and the solar heat can be given to the heat-transfer medium by means of these heat-transfer-medium pipes.

As FIG. 5 shows, multiple heliostats 16 are provided concentrically around the supporting post 14. The heliostats 16 are divided into a group of heliostats 16 b located near the supporting post 14 and another group of heliostats 16 a located far away from the supporting post 14. Each of the heliostats 16 b located at nearby positions casts a reflected light R11 of the sunlight S onto the center reflector 13 whereas each of the heliostats 16 a located at faraway positions casts a reflected light R12 onto the receiver 11 a provided at the upper position on the supporting post 14. In addition, the reflected light R12 that has cast onto the center reflector 13 is collected by the receiver 12 located at the lower position.

The heliostats 16 b located at nearby positions and the heliostats 16 a located at faraway positions as well as the receiver 11 a and the center reflector 13 are individually adjusted so that each of the light-receiving areas formed on the receiver 11 a and on the center reflector 13 can be so small as to make its illuminance stronger. To achieve small light-receiving areas, each of the incident angles of the incident lights is a right angle or an angle close to a right angle. Specifically, as in the case of the first embodiment, the incident angle is within a range from 75° to 105°.

The center reflector 13 is equipped with a cleaning means G that cleans a wall surface (reflector-mirror surface) of the center reflector 13. As FIG. 6 shows, the cleaning means G is formed in an arc shape that can fit the wall surface 13 c of the center reflector 13. The cleaning means G includes a frame f, a cleaning robot GR, and a driving device m2. The lower-end side of the frame f is supported on the supporting post 14. The cleaning robot GR is attached to the frame f so as to be capable of moving along the frame f. The driving device m2 moves the frame f, to which the cleaning robot GR is attached, along the circumferential direction of the center reflector 13.

The frame f is formed in a narrow width so as to reduce the blocking of the reflected light that is cast onto the center reflector 13. In addition, the frame f is made of a heat-resistant alloy so as to resist high-temperature heat produced by the reflected light cast by the heliostats 6. Incidentally, the alloy is one of light weight. Some examples of alloys usable for this purpose are high-nickel/iron alloys such as Inconel® alloys and Hastelloy® alloys.

The upper-end side of the frame f is connected to a driving device m1 that is provided on the ring-shaped perimeter edge portion of the center reflector 13. The driving device m1 and the driving device m2 provided on the lower-end side of the frame f move the frame f. Note that the frame f may be one of cantilevered type with the driving device m2 provided on the supporting post 14 being the only support for the frame f.

The cleaning robot GR includes a cleaning device n, which sprays a cleaning liquid onto the wall surface 13 c of the center reflector 13. The cleaning device n includes a spray nozzle and the like for the purpose of washing, with water, the dust or the like that adheres to the wall surface 13 c. In the surrounding area of the cleaning device n, a synthetic-resin cover is provided to prevent the washing liquid from leaking out. The cleaning liquid is re-collected and filtered by a filtration device, and then is sprayed by the nozzle. To put it differently, the liquid is circulated and re-used. Alternatively, the nozzle may spray either hot water or steam obtained by using the heat of the heat-transfer medium (molten salt) for power generation.

The cleaning means G is designed to operate while none of the reflected lights R11 and R12 enter the reflector, e.g., at night. The cleaning means G is made to operate automatically at night by a computer.

Note that, while the heliostats 6 are casting the solar heat onto the center reflector 13, the cleaning robot GR is held at a position of either the upper-end side or the lower-end side of the frame f so that the cleaning robot GR can avoid the influence of the solar heat. In the Northern hemisphere, the heliostats located at the northern side of the center reflector 13 receive stronger sunlight than the heliostats located at the southern side thereof. Accordingly, the frame f is moved to the southern side of the center reflector 13, and thus both the influence of the solar heat and the occurrence of the blocking can be reduced.

In this embodiment, the supporting post 14 is equipped with the receivers 11 a and 12, and is also equipped with the center reflector 13. The reflected light R12 coming from the heliostats 16 b located near the supporting post 14 is cast onto the center reflector 13 whereas the reflected light coming from the heliostats 16 a located far away from the supporting post 14 is cast onto the receiver 11 a. Accordingly, the reflected lights coming from heliostats located in sections from a position near the supporting post 14 to a faraway position can be received in a highly efficient manner by the receivers 11 a and 12.

Accordingly, even if the heliostats are provided in an area (measured in terms of the radius) that is approximately the same as the corresponding area in conventional cases, the amount of power generation can increase as FIG. 11 shows. In addition, a significant increase in power generating capacity can be achieved by a larger-scale power generation device of this kind.

Embodiment 3

The device of this embodiment, as FIG. 7 shows, includes a receiver 21 a that is provided in an upper-side portion of a columnar body 25. In addition, supporting posts 24 are provided so as to open downwards to form a pyramid shape. A center reflector 23 is provided in the space thus formed under the supporting posts 24. A receiver 22 is provided below the center reflector 23.

A light collecting portion 22 b is formed on the upper side of the receiver 22. The light collecting portion 22 b has a crucible-like shape, and collects the solar heat reflected by the center reflector 23. A heat exchanging portion 22 c is formed on the lower side of the receiver 22. A heat-transfer-medium pipe 22 f is wound around the external circumference of the heat exchanging portion 22 c. The internal wall of the light collecting portion 22 b has a mirror surface so that the solar heat can be reflected inside the light collecting portion 22 b and can be introduced into the heat exchanging portion 22 c located below.

An opening portion 22 a is formed in the light collecting portion 22 b of the receiver 22 that is provided below the center reflector 23. A dust-prevention means g is provided on the opening portion 22 a. While the sunlight (solar heat) can pass though the dust-prevention means g, dust such as sand cannot pass through the dust-prevention means g. An example of the dust-prevention means g is a lid plate made of borosilicate glass or the like.

Without the dust-prevention means g, dust such as sand may enter the inside of the light collecting portion 22 b of the receiver 22 through the opening portion 22 a of the light collecting portion 22 b, and may dirty the mirror surface and the heat exchanging portion 22 f, resulting in lower light-collection efficiency and lower heat-exchange efficiency. The dust-prevention means can prevent the entry of the dust, and thus the lowering of the efficiencies can be prevented from happening. The receiver 22 has a height of approximately 5 m, so that it is not easy to clean the inside of the receiver 22. Providing the dust-prevention means g can save the user the trouble of performing the maintenance work for the receiver 22.

In this embodiment, the reflected light coming from each of the heliostats located at faraway positions is received by the receiver provided on the upper side, whereas the reflected light coming from each of the heliostats located at nearby positions is received firstly by the center reflector provided on the lower side, and then passed onto the receiver provided on the ground. Accordingly, an incident angle that is close to a right angle can be achieved for the sunlight that is cast by the heliostats located in sections from nearby positions to faraway positions. Accordingly, the intensity of the light with which the light receiving surface of the receiver is irradiated becomes stronger. The strong intensity of the light allows more steams to be generated, resulting in an increase in the power generating capacity.

In addition, the pyramid-shaped supporting posts provided to support the center reflector gives higher strength to the supporting structure, resulting in an improvement both in the quake resistance and in the wind resistance.

In addition, the dust-prevention means is provided to cover the light entrance of the receiver provided below the center reflector. This prevents the lowering down of the heat exchange efficiency between the molten salt and the reflected light, which would otherwise be caused by dust such as sand dirtying the mirror surface of the inside of the light collecting portion 22 b.

In addition, the receiver provided below the center reflector includes the light receiving portion with a crucible-like shape, a difficult shape for the heat of the incident light to escape from. Consequently, higher thermal efficiency can be achieved. 

1. A solar heat power generation device comprising: a supporting post including a receiver that receives sunlight; and a plurality of heliostats which are provided so as to surround the supporting post and which reflect the sunlight towards the receiver, the solar heat power generation device characterized in that the supporting post includes at least two receivers that are arranged in the up-and-down direction, the receiver provided at an upper-side position receives reflected lights coming from the heliostats located at faraway positions, and the receiver provided at a lower-side position receives reflected lights coming from the heliostats located at nearby positions.
 2. The solar heat power generation device according to claim 1 characterized in that, when the light intensity of a reflected light received by a receiver with a 90-degree incident angle is 100%, each of the receivers receives the reflected lights coming from heliostats located at positions such that a light intensity of 60% or higher is achieved by each reflected light received by the corresponding receiver.
 3. The solar heat power generation device according to claim 1 characterized in that an incident angle of the reflected light reflected by each heliostat located far away from the supporting post towards the receiver provided at the upper-side position is set at 75° to 105°, and an incident angle of the reflected light reflected by each heliostat located near the supporting post towards the receiver provided at the lower-side position is set at 75° to 105°.
 4. A solar heat power generation device comprising: a supporting post including receivers that receive sunlight; and a plurality of heliostats which are provided so as to surround the supporting post and which reflect the sunlight towards the receivers, the solar heat power generation device characterized in that one of the receivers is provided at an upper-side position on the supporting post, the one receiver receiving reflected lights coming from the heliostats located at faraway positions, and a center reflector is provided at a lower-side position on the supporting post, the center reflector receiving reflected light coming from the heliostats located near the supporting body, and another one of the receivers is provided below the center reflector, the other receiver receiving the sunlight having been reflected by the center reflector.
 5. A solar heat power generation device characterized in that at least three supporting posts are assembled together to form a pyramid shape, a columnar body is provided so as to extend upwards from upper-end sides of the supporting posts, a center reflector is fixed to the supporting posts that have been assembled together to form the pyramid shape, in addition, receivers are provided below the center reflector and on the columnar body, the receiver provided on the columnar body receives reflected lights coming from heliostats provided far away from the supporting posts, and the center reflector receives reflected lights coming from heliostats provided near the supporting posts, and the receiver provided on the supporting posts receives the lights passed on to the receiver by the center reflector.
 6. The solar heat power generation device according to claim 4 that includes: the supporting post equipped with the center reflector; and the plurality of heliostats provided so as to surround the supporting post, the solar heat power generation device characterized by comprising: a frame formed in an arc shape that fits a wall surface of the center reflector having a semicircular arc sectional shape, the frame having one of its ends supported by the supporting post; a cleaning robot which is attached to the frame so as to be capable of moving along the frame; and moving means for moving the frame with the cleaning robot in a circumferential direction of the center reflector; and the solar heat power generation device characterized in that the cleaning robot includes a spray device that sprays a cleaning liquid onto the wall surface of the center reflector.
 7. The solar heat power generation device according to claim 4 characterized in that the receiver provided below the center reflector includes a cone-shaped light receiving portion, and dust-prevention means for allowing the transmission of the sunlight therethrough but for blocking entry of dust such as sand is provided to cover a light entrance for the sunlight formed in the light receiving portion. 